As the other educator has correctly mentioned, allusions are indirect references to people, places, and things of historical, political, or social significance.
In Part Three, an example of allusion is a name uttered by Arthur Berg, the fifteen-year-old leader of a fruit-stealing gang:
Arthur had moved on to Rudy. “And you’re the Jesse Owens one, aren’t you?”
Jesse Owens was an American runner known for his speed: he won four Gold medals at the 1936 Berlin Olympics in Germany. Through his amazing feats as an athlete, Jesse Owens, a black man, invalidated the basic tenets of Hitler's Aryan supremacist ideology. In the reference above, Rudy is said to be as fast as Jesse Owens. Liesel argues that Rudy is fast enough to be a part of Arthur Berg's fruit-stealing gang, alluding to Rudy's great speed.